Structural valorization/characterization of lignin and recovery/ recycling of the protic ionic liquid 2-HEAA on sugarcane bagasse pretreatment

Abstract

Although not much explored, using protic ionic liquids (PIL's) might be an alternative to fractionate lignin from sugarcane bagasse and potentially change its ultrastructure. The vast majority of works in the literature use aprotic IL's, whose production is far more expensive than the protic ones. In this work, the pretreatment process with PIL will be evaluated. The Ph.D. project - on its early stage - started up with a screening to investigate the best combination of cation/anion (among twelve PIL's) and found that 2-hydroxyethylammonium acetate, 2-HEAA, efficiently extracted lignin from bagasse with minimal loss of carbohydrates dissolved in the ionic liquid and provided high cellulose and hemicelluloses conversions. Then, the pretreatment process is undergoing a parameter optimization using design of experiments. Parameters such as pretreatment time, temperature, solid:liquid ratio and water content need to adjusted to provide maximum carbohydrates conversion on enzymatic hydrolysis and lignin extraction. After the optimization, the focus will be towards lignin recovery upon anti-solvent addition. The lignins isolated in such way will be comprehensively analyzed and characterized at the Imperial College London. Such characterization may ultimately shed light onto possible utilizations and derivatizations of lignin to add up value to this byproduct. The next key step in the process development will be the recycling of the ionic liquid. Structural characterizations of 2-HEAA before and after the pretreatments and recycles will help us understanding and correlating the presence of biomass compounds (or biomass degradation products) with the overall performance of the PIL measured by carbohydrates conversion on enzymatic hydrolysis, as well as give us some hints on how to minimize PIL losses in the process.